He needs this.
It is an illogical burning messy painful hard need that eats at him, filling every space that isn't filled with the void that Vulcan's destruction has left within. Uhura, this ship, meditation, nothing else can give him release like this can.
He cannot understand himself. Since the two things he had once called home, his mother and his planet, left him Spock has spent hours trying and failing to meditate logically and peacefully in the way he once did as he breathed. Anger, desperate sadness, pain; all curl within him, a testimony to the harsher things he was taught to cast aside as a young child.
But there is nobody left to teach him that. The ten thousand Vulcans have left for the new colony. He has remained on the USS Enterprise and suffered as quietly and stoically as one could logically hope for.
Uhura- Nyota, he reminds himself- is gentle, soft, supportive. She strokes his head, cradles it as if he were made of glass and whispers nothing at all in his ear over and over. It soothes him but never for long. Her cool skin only wipes away the burns on his skin for a day, two days, until he becomes aflame again.
Jim Kirk is none of those adjectives applied to the woman he loves. It seems- on the surface- that he was little changed by the mission, though what goes on under when he looks out the deck off duty with a new and philosophical glint in his eyes is anyone's guess, and Spock still does not guess. He continues to dive headfirst. He still showcases breathtakingly cocky overconfidence. He is still himself.
The passion proves, Spock decides, an excellent outlet.
Kirk ("Call me Jim," he had insisted with a smirk. He cannot, not here.) pushes back beneath him as they writhe on the sheets in Spock's room, computer controlled heat to maximum with the driest air he could manage. Spock's face is in his shoulder, eyes tight shut as he struggles to hold Kirk down despite the younger man's efforts to throw him. With a barely-contained growl he tightens his grip enough to bruise and Kirk finally relents, choosing to show his displeasure by biting Spock's shoulder instead. It is ineffective. Spock relishes it, each sting like a hole through which his emotions exit, leave him in peace.
The clothes they were wearing lie in tatters on the floor, ripped in a fit of anger as the conversation- Kirk thrusts up into his groin and Spock forgets the topic they were on at the time in a spike of lust he automatically starts to restrain, unfamiliar- turned for the worse.
As white builds behind his closed eyes he pushes his hands down, leaving marks as he goes, marks that show what has happened, what he is. Needs. They come together, now- a practiced dance, releasing and leaving a few moments of total sensory deprivation as Spock collapses exhausted on Kirk.
He can breathe again, for now.